1. Field
The present application relates to a structured illumination apparatus, a structured illumination microscopy, and a structured illumination method.
2. Description of the Related Art
Patent Document 1 (U.S. Pat. No. 6,239,909) discloses an example in which a structured illumination microscopy is applied to a fluorescent observation. In a method of Patent Document 1, a light flux that exits from a coherent light source is split into two light fluxes by a diffraction grating, and those two light fluxes are individually focused on mutually different positions on a pupil plane of an objective lens. The two light fluxes exit from the objective lens as collimated light fluxes with different angles, and overlap each other on a sample plane to form interference fringes. Accordingly, the sample plane is subjected to structured illumination. Further, in the method of Patent Document 1, images of sample images are obtained using different phase of the structured illumination, and separated for frequency components and demodulated from the plurality of obtained images by the method described in the U.S. Patent Document 1.
Note that as a method of shifting the phase of structured illumination in steps, there are a method in which a wedge-shaped prism is inserted into one of the above-described two light fluxes and moved in steps in a direction perpendicular to an optical axis, a method in which a diffraction grating is moved in steps in a direction perpendicular to a grid line, a method in which a sample is moved in steps in a pitch direction of structured illumination, and the like.
However, when an optical element is moved in steps, a certain period of time is required for moving and stopping of optical element at an appropriate position, so that it is difficult to reduce a period of time to take all of the required images. Particularly, when a sample to obtain the images is a live organism specimen, there is a chance that a structure of the sample changes every second, so that the obtainment of images should be performed as fast as possible.
Further, as an application of technique utilizing the interference fringes (Patent Document 1), a technique of turning a beam that contributes to the interference fringe into three beams (Non-Patent Document 1: Mats G. L. Gustafsson et al., “Doubling the lateral resolution of wide-field fluorescence microscopy using structured illumination”, Proceedings of the SPIE—The International Society for Optical Engineering, Vol. 3919, pp. 141-150, 2000) has also been proposed for achieving a super-resolution effect in both of an in-plane direction and a depth direction of a sample. This is because, if three beams are used, a stripe pattern of structured illumination can be generated not only in the in-plane direction but also in the depth direction. However, in that case, the number of images required for the aforementioned separating calculation is increased, so that it can be considered that the necessity of increasing the speed of obtaining images is particularly high.